Ford said it has hired outside experts to investigate its vehicle fuel economy and testing procedures after employees raised concerns, and did not know whether it would have to correct data provided to regulators or consumers.

The issues involving Ford’s testing processes do not involve the use of so-called defeat devices – hardware and software designed deliberately to deceive government emissions tests, Kimberly Pittel, Ford’s group vice president for sustainability, environment and safety engineering, told Reuters.

The automaker since last fall has been investigating concerns raised by employees that incorrect calculations were used to translate test results into the mileage and emissions data submitted to regulators, Pittel said.

Ford has hired the law firm Sidley Austin to lead an independent investigation into possible discrepancies in calculations used to produce emissions and fuel economy figures, Pittel said. The company is using an independent laboratory to conduct testing.

The investigation has started with testing of the 2019 Ranger pickup truck, and the company expects data back next week, Pittel said.

She said it was not clear what impact the review will have on advertised mileage or fuel economy data submitted to regulators, nor is it clear how many vehicles could be affected if Ford is required to revise the data.